Power Macintosh G4 450MHz (AGP)

A major update of similar computer, now included AGP graphics card, 100MHz system bus, and, in high-end models, DVD-ROM or DVD-RAM drives. Earlier ones had ZIP and CD-ROM drives. More, this model was ready for AirPort card, which allowed to use wireless networking. Some 450MHz units (pre February 2000) are underclocked 500MHz because Motorola couldn't deliver enough CPU chips for popular model.

Overclocking

As in all Power Macs, it requires some soldering, so I take no responsibility if it won't work. I have no experience in OCing these units, I don't know nor tried to discover safety boundaries of it, so do it on your own responsibility!. According to what's in my CPU module and on the Internet, you should remove CPU card and flip it to see the PCB connector. It should look like this:

There are 3 regions: A is a CPU voltage selector, B is an actual overclocking setting, C is a L2 Cache signal selector.

Generally, the higher voltage is used, the higher frequency can be reached, but more (LOTS more) heat will be dissipated and the CPU may be destroyed.

Now, the explaination of the regions. Every combintation of 4 resistors form 4 bits of configuration. Let's begin with B - CPU Multiplier:

133MHz Bus modding As I heard, it doesn't work with most units. You can clock everything in this Mac to work with 133MHz system bus. 133MHz memory is required and most PCI cards may not work. More, these Macs use bus clock to drive almost everything, even to run system clock, so it will tick faster without other firmware mods (read here). To find things responsible for system bus, look under the mainboard - they're on its bottom:

R435 - FS0 R434 - FS1 R433 - FS2 R432 - SSON

According to SG500 datasheet (here), working with this at 133MHz IS an actually overclocking the IC itself.